This invention relates generally to a resin sensor for water treatment, and more particularly to an improved automatic control for the regeneration of a water softener wherein the pressure of the resin is sensed to determine when regeneration should be effected.
As indicated in U.S. Pat. No. 4,385,992 assigned to the assignee of this application, there are several different approaches to the control of the regeneration of water softener resin. An example of an automatic sensing water softener control is found in U.S. Pat. No. 3,574,330 also assigned to the assignee of this application. These previously mentioned U.S. patents as well as U.S. Pat. Nos. 4,332,678 and 3,479,864 rely on measuring resin expansion by means of swelling of the resin in a chamber which will permit some type of resin expansion. In the one embodiment in U.S. Pat. No. 3,479,864 where a Bourdon tube is employed, there is no consideration for eliminating differences in water pressure from the resin pressure measured. In U.S. Pat. Nos. 3,574,330 and 4,385,992 a sampling cell is provided wherein the resin is allowed to expand upon regeneration and to contract upon depletion, and a plunger in the cell is permitted to extend inwardly to sense the volume of the resin.
In contrast, the sensor of this invention does not sense the resin volume expansion but instead confines the resin in a container from which the resin pressure is measured by its force on the container.